1. Field of the Invention
The present invention is directed to a method for arresting or inhibiting the growth of malignant or premalignant cells in Kaposi's Sarcoma lesions. The invention is further directed to a method of blocking or inhibiting the activity of cellular vascular permeability factor or factors in vascular cells.
2. Background Information
Various forms of Kaposi's Sarcoma are clinically recognized. These include classical [W. A. Reynolds et al. Medicine 44, 419 (1965)], African endemic [J. F. Taylor et al. Br. J. Cancer 26, 483 (1972)], immunosuppressive therapy-associated [I. Penn Transplantation 27, 8-11 (1979); D. I. Greenfield et al. J. Rheumatol. 13, 637 (1986)], and an aggressive form of Kaposi's Sarcoma frequently observed in young HIV-1 infected homosexual men [K. B. Hymes et al. Lancet ii, 598 (1981); B. Safai al. Ann. Intern. Med. 103, 744 (1985)]. Despite the clinical and epidemiological distinct forms, all are histologically similar, and exhibit microvascular proliferation (angiogenesis) in the initial stage of lesion development, which is soon followed by the presence of proliferating spindle cells, edema, and infiltration by multiple cell types [N. S. McNutt et al. Am. J. Pathol. 111, 62 (1983)].
The present inventors have previously developed in vitro systems for the long-term culture of Kaposi's Sarcoma-derived spindle shaped cells using conditioned media from HTLV-I or HTLV-II infected and immortalized CD4 positive T cells or from activated peripheral blood mononuclear cells, to facilitate cell growth [S. Nakamura et al. Science 242, 426 (1988)] and in vivo systems which simulate the formation of Kaposi's Sarcoma [S. Nakamura et al. Science 242, 426 (1988); S. Z. Salahuddin et al. Science 242, 430 (1988)]. These cells produce several lymphokines which establish the in vitro growth of these cells. They include interleukin 6 (IL-6) [S. A. Miles et al. Proc. Natl. Acad. Sci. USA 87, 4068 (1990)], interleukin 1 (IL-1), and tumor necrosis factor .alpha. (TNFe) [S. Nakamura et al. Science 242, 426 (1988)]. However, the most active growth factor for the Kaposi's Sarcoma spindle cells is a 30 kD protein [S. Nakamura et al. Science 242, 426 (1988)] recently purified and now under analysis. The effect of the 30 kD lymphokine is augmented by corticosteroids, but the mechanism for this interaction is unknown. In addition to these T cell-derived lymphokines, one viral protein, the HIV-1 regulatory protein called Tat, has also been shown to have similar growth promoting effects on these cells [B. Ensoli et al. Nature 345, 84 (1990)], and its effect is at very low concentrations.
These cultured Kaposi's Sarcoma spindle cells obtained from different patients and from various tissues/organs themselves produce various cytokines which affect their own growth, growth of other cells, and other effects which lead to biological changes resembling Kaposi's Sarcoma. These cytokines include: basic fibroblast growth factor (bFGF)-like factor, platelet-derived growth factor (PDGF), IL-1, granulocyte-monocyte colony stimulating factor (GM-CSF) [B. Ensoli et al. Science 243, 223 (1989)], IL-6 IS. A. Miles et al. Proc. Natl. Acad. Sci. USA 87, 4068 (1990)], and a vascular permeability factor(s). The cultured human Kaposi's Sarcoma cells induce vascularization on chicken chorioallantoic membranes (CAM), and when transplanted into nude mice they induce vascular hyperpermeability and resultant edema, angiogenesis, and the development of Kaposi's Sarcoma-like lesions of murine origin [S. Z. Salahuddin et al. Science 242, 430 (1988)]. These results combined with some clinical observations suggest that Kaposi's Sarcoma is not a simple malignancy, but at least in its early stages is more likely a reactive lesion, developing in response to endogenous soluble mediators [J. Costa and A. S. Rabson Lancet i, 58 (1983); J. J. Brooks Lancet ii, 1309 (1986)].
Kaposi's Sarcoma is currently treated with various cytotoxic agents such as vinblastine, bleomycin [P. A. Volberding et al. Ann. Intern. Med. 103, 335 (1985); P. Gill et al. Am. J. Oncol. 13, 315 (1990)], suramin [A.M. Levine et al. Ann. Intern. Med. 105, 32 (1986)], or with cytokines such as interferon .alpha. (IFN.alpha.) [S. E. Krown et al. N. Engl. J. Med. 308, 1071 (1983)]. Both of these forms of therapy may affect many cell functions. More recently an angiostatic compound, pentosan polysulfate, has also been employed, but many recently described potential angiostatic compounds [R. C. Gallo Quatrieme Colloque Des Cent Gardes (Proceedings, Biomedical Research Strategy on AIDS) 113 (1989); B. Ensoliet al. Hematol. Oncol. Clin. North Am. 5, 281 (1991); S. Taylor and S. Folkman Nature 297, 307 (1982); J. Folkman et al. Science 243, 1490 (1989); Jo Folkman and D. E. Ingber Ann. Surg. 206, 374 (1987); T. E. Maione et al. Science 247, 77 (1990)] still remain to be clinically tested. One of these was the compound of the present invention, SP-PG, a naturally occurring sulfated polysaccharide-peptidoglycan produced by a specific species of the bacterium Arthrobacter, AT-25. SP-PG has been reported to inhibit the development of vascularization in CAM assays and the growth of subcutaneously inoculated solid tumors (which require angiogenesis for their growth), while not affecting growth of ascites tumor cells of the same origin [N. Tanaka et al. Cancer Res. 49, 6726 (1989 ) ].
SP-PG is also known as DF4639. U.S. Pat. No. 4,900,815 (the entire disclosure of which is hereby incorporated by reference) describes the anti-tumor and anti-angiogenic effects of DF4639. However, previous to the present invention, the ability of this drug to arrest or inhibit the growth of cells in Kaposi's Sarcoma lesions and the ability of SP-PG to arrest or inhibit the growth of the lesions themselves were not known or suspected. Likewise, the ability of SP-PG to block or inhibit the activity of cellular vascular permeability factors was neither known nor suspected.
Although the anti-angiogenesis activity and the anti-tumor activity of SP-PG were both previously described in U.S. Pat. No. 4,900,815, the previous inventors did not test the drug on Kaposi's Sarcoma or suggest that it might inhibit the growth of Kaposi's Sarcoma lesions. It is believed that this is due, in part, to the fact that the patent deals with the effect of SP-PG on solid tumors and the Kaposi's Sarcoma lesion is not considered to be a "classical" solid tumor. It is not comprised entirely of tumor cells; normal cells of various types are present in Kaposi's Sarcoma lesions. In any event, it was not obvious to the scientists skilled in the art who were familiar with the activities of DF 4639 (SP-PG) that the drug would inhibit development of Kaposi's Sarcoma lesions. Nor did these scientists foresee that it should even be proposed as a possible treatment for Kaposi's Sarcoma.
Therefore, with respect to its antitumor and antiangiogenic activities, the present inventors were the first to realize the use of the drug in the treatment of Kaposi's Sarcoma patients. Furthermore, there was no indication from previously obtained data using the drug that it affected vascular permeability.
The present inventors were able to demonstrate that the edema sometimes associated with Kaposi's sarcoma (KS) in patients could be induced by AIDS-KS cells inoculated subcutaneously into nude mice. This effect of the KS cells had not previously been demonstrated. The present inventors were then able to demonstrate that DF 4639 (SP-PG) could block this activity. Since cellular mechanisms involved in inducing or blocking angiogenesis are not well understood and since mechanisms involved in inducing or blocking vascular permeability are not well understood, there was no reason to suspect a common mechanism of induction of angiogenesis or blocking increased vascular permeability and no reason to assume that a drug that inhibited angiogenesis would also block the increased vascular permeability which leads to edema.
Since the anti-angiogenic activity of SP-PG responsible for an anti-tumor effect was believed to target cells of vascular origin [N. Tanaka et al. Cancer Res. 49, 6726 (1989)], the present inventors initiated tests of SP-PG in in vitro and in vivo Kaposi's Sarcoma systems developed at the National Cancer Institute (NCI) [S. Nakamura et al. Science 242, 426 (1988); S. Z. Salahuddin et al. Science 242, 430 (1988)]. Human recombinant interferon .alpha. (IFN.alpha.) [S. E. Krown et al. N. Engl. J. Med. 308, 1071 (1983)], suramin [A.M. Levine et al. Ann. Intern. Med. 105, 32 (1986)] and pentosan polysulfate [L. Biesert et al. AIDS 2, 449 (1989)] were also studied in parallel experiments. The results of these tests are discussed below.